The present invention generally relates to hydraulic controls and more specifically to the hydraulic controls for attachments to skid steers, loader tractors and other work vehicles.
Skid steers, loader tractors and other commercial work vehicles are commonly used for many industrial, agricultural, and landscaping operations. These work vehicles typically have two laterally spaced loader arms that extend in front of the vehicle that are adapted to attach to a wide variety of attachments. Commercial work vehicles may also have a three point hitch at their back end. A number of attachments can be selectively attached and detached from the loader arms or the three point hitch to make these work vehicles applicable to a wide variety of applications. For example, a bucket is commonly provided to dig, dump and transport loose materials such as dirt, sand and gravel. The loader arms are hydraulically driven to raise and lower the attachment and pivot the attachment about a horizontal axis.
Skid steer loaders and other work vehicles commonly have a single hydraulic hook-up which comprise a pair of couplings (one for pressurized hydraulic flow and the other for rated flow) that can be utilized by the attachment for any desired purpose. A control lever is provided in the operator cab for controlling the hydraulic flow to the attachment through the hydraulic couplings. The common uses of the hydraulic pump include tilting the attachment left or right about a vertical axis to effect a windrow and/or to direct dirt, gravel or debris, or alternatively hydraulically driving an engaging device such the rotary rake of a as a rock raking attachment.
Although a single hydraulic hook up is sufficient for many of the applications, it is often insufficient for certain attachments where it is required or desirable to have hydraulic control over more than one function, such as rotary broom attachments. Rotary broom attachments often include: (1) a hydraulic cylinder for tilting the broom left or right about a vertical axis to direct swept debris or effect a windrow and (2) a hydraulically driven motor that rotates the broom to sweep material. Heretofore, the prior approach of controlling two separate hydraulic functions with a single power source has been to use an electronically operated solenoid that switches between the two functions. However, this approach has significant drawbacks. One drawback is that electrical wiring, electrical hook-ups and electrical couplings are necessary to operate the solenoid. These electrical components increase the time and difficulty of attaching and detaching attachments. Loose wires can also break or sever when not properly secured or when not properly located out of the way when not in use. Due to the environment at which attachments operate, these electrical components are also often subject to wear, poor connections and the like. In view of the foregoing, electrical hook-ups, wiring and couplings have lead to much aggravation for work vehicle operators, require frequent replacement and are not desirable.
It is an object of the present invention to eliminate or reduce the need for electrical wiring hook ups, electrical couplings, and electrical wiring on attachments for work vehicles that have more than one hydraulically powered function.
In accordance with this objective the present invention provides an attachment that has a hydraulic circuit that is responsive to hydraulic signals (e.g. as result of hydraulic flow being reversed) that selectively operates one of the hydraulic functions when one signal is received and the other hydraulic function when the other hydraulic signal is received.
According to one aspect, the present invention is directed toward an attachment for selective attachment to and detachment from a work vehicle. As is conventional, the work vehicle has a hydraulic pump for generating a working output and a hydraulic sump and the working output controlled by the operator of the work vehicle to selectively provide two different hydraulic signals. The attachment includes a mounting structure adapted to attach and detach the attachment to the work vehicle. The attachment further includes a first hydraulic actuator performing a first work operation a second hydraulic actuator performing a second work operation (thus two hydraulic functions). A hydraulic circuit connects the working output of the work vehicle with the first and second hydraulic actuators. The hydraulic circuit including a primary circuit directing the working output to the first hydraulic actuator and a secondary circuit directing the working output to the second hydraulic actuator. To control flow between hydraulic function, the hydraulic circuit further comprises a diversion valve (in the preferred form of a check valve) diverting working output through the secondary circuit in response to one of the hydraulic signals.
It is a further aspect of the present invention that the second hydraulic actuator is a hydraulic cylinder requiring flow to it to be reversed in order to have a reciprocating stroke. To switch or reverse the flow, a hydraulic switch is provided that is responsive to hydraulic pressures in the hydraulic circuit to control hydraulic flow to the hydraulic cylinder and expand or retract the cylinder as desired.
According to a preferred implementation, the hydraulic circuit comprises a pair of hoses for hydraulic coupling to the work vehicle and a hydraulic sequencing block. One of the hoses is directly connected to the first actuator in the form of a hydraulic rotary motor (that may power a rotary broom for example). The hydraulic sequencing block comprises
(a) a first port hydraulically connected with the first hydraulic hose,
(b) a second port hydraulically connected with the rotary motor;
(c) a pair of third and fourth ports hydraulically connected to the hydraulic cylinder for reciprocating the hydraulic cylinder;
(d) a diversion valve arranged between the first and second ports adapted to divert hydraulic working flow through a bypass conduit to one of the third and fourth ports for operating the hydraulic cylinder;
(e) a hydraulic switch arranged in the bypass conduit adapted to switch the working flow between the third and fourth ports, the hydraulic switch adapted to be responsive to increased hydraulic pressure in the working output as a result of the hydraulic cylinder reaching ends of its linear reciprocating movement; and
(f) a vent conduit venting to the second port, routed through the switch to one of the third and fourth ports for venting flow from the hydraulic cylinder out through the second port.
Other objectives and advantages of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.